A highly reliable timing and frequency reference is essential for wireless communication systems that use either digital or analog technologies. Synchronization to a standard timing and frequency reference is particularly important when the communication system employs multiple digital or analog components. Earth orbit satellite networks are examples of these type of communication systems.
Time and frequency synchronization of a terrestrial receiver to a GPS satellite system is known, as is evidenced by, for example, Absolute Time Corporation's Model 100A/B GPS Clock; Datum, Incorporated's Model bc627AT GPS Satellite Receiver; Hewlett-Packard's Models HP 58000A and HP 58503A; and TrueTime's Model GPS-705 Receiver. In these conventional systems, the terrestrial receiver accomplishes time and frequency synchronization by locking itself to signals from the GPS. This locking feature is implemented by disciplining the receiver's reference oscillator to input time and frequency signals received from the GPS. The synchronization can be remotely monitored for accuracy. If an inaccurate condition is detected, time and/or frequency correction is allowed. However, the correction techniques require intervention by ground commands.
Currently, earth orbit satellite networks do not employ this technique of time and frequency synchronization using a GPS system. Thus, there is a need for a system which maintains the synchronization between a satellite's time and/or frequency and that of the GPS system.